This invention pertains generally to steam reformer furnaces. More particularly, the invention is directed to such a steam reformer furnace wherein the steam reforming of hydrocarbons is conducted in a plurality of vertically oriented tubes which pass through the firebox of the furnace. The tubes are connected at their top to an inlet header and at their bottom to an outlet header. The aperture, through which each tube exits the firebox, is partially closed off by sliding steel base plates. A cast refractory seal is formed around the tube at the point of said base plates.
Reforming furnaces are well known in the prior art. However, these prior art steam furnaces have several drawbacks, including: (a) air leakage of the furnace firebox with the attendant loss of furnace energy efficiency, (b) the detrimental spacing tolerance between the vertical tubes of the furnace and the outlet aperture of the firebox with the attendant room for vibration of the tubes during operation of the furnace, (c) the failure to provide for the thermal expansion of the vertical pipes and the outlet header with respect to the outlet apertures, and (d) the serviceability of prior art seals at such outlets from the firebox.
In U.S. Pat. No. 3,607,130 to Worley et al. which is assigned to the assignee of this invention, a steam reformer furnace is described which provides a header and tube assembly specifically directed to some of the problems mentioned above. Particularly, Worley et al. provide a flexible upper mounting for the vertical tubes, as well as a flexible inlet connection to the tubes from the upper header. However, as shown in FIG. 2, the patent is not directed to an outlet seal for the vertical tubes.
U.S. Pat. No. 3,414,052 to Chojnowski et al. teaches the use of a compressible refractory packing for the seal of a heat exchange tube at the passage through the wall of a recuperative heat exchanger. The use of such a packing does not lend itself to readily being recast during maintenance operations, nor does the compressive feature of the heat exchanger seal provide sufficient damping for the seals in a reformer furnace seal. U.S. Pat. No. 3,475,135 to Gargominy describes a reformer furnace wherein the seal of the vertical tube and the floor of the furnace firebox is provided by means of a plurality of pellets of particulate fireproof material and a rigid bar of the same fireproof material. The former fails to prevent the loss of heated gases, while the latter does not solve the tolerance or vibration dampening problems of reformer furnaces.
Other prior art teachings of furnace seals of general interest include U.S. Pat. No. 2,987,382, Endter et al.; U.S. Pat. No. 3,030,092, Hildenbrand; U.S. Pat. No. 3,406,804, Breckenridge; U.S. Pat. No. 3,617,227, Beggs and U.S. Pat. No. 3,838,536, McCoy.